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Started programming on a ZX spectrum in the 80's and have moved through Assembly, Turbo Pascal, C++, C#, Fortran. My main area of focus is engineering and scientific computing like numerical methods and 3D graphics.


Jun
9
answered Rate of change of a vector
Jun
9
answered Uniform Circular Motion and Centripetal Acceleration
Jun
9
comment Curve of a rod bent by force on both sides
In terms of axial force, the amplitude is $$f^2 \approx \frac{4}{\pi^2} \frac{F \ell^2}{A E}$$.
Jun
9
comment Understanding why a problem was solved a certain way
Yes, you got it.
Jun
9
comment Curve of a rod bent by force on both sides
As an approximation of constant length, the amplitude is found to be $$f^2 = \frac{4 \ell \delta}{\pi^2 }$$ where $\delta$ is the axial displacement.
Jun
9
answered Understanding why a problem was solved a certain way
Jun
6
comment Why do heavier objects fall faster in air?
So after integration the resulting function needs inversion.
Jun
6
comment Why do heavier objects fall faster in air?
@JanHudec when integrating over speed as an independent variable then the limits have to be in speeds. You are answering the question, how long does it take to move from speed 1 to speed 2? Why is there confusion on this issue? $\int_0^v \ldots {\rm d}u$ is the proper form of the integral.
Jun
6
comment Why do heavier objects fall faster in air?
Shouldn't the limits be: $$t_2 - t_1 = m \int_{v_1}^{v_2} \frac{d v}{mg -cv^2}$$ and not $\int_0^t$
Jun
6
comment Defy gravity torques with gyroscopes?
Have you included the gravity forces in the total torque about the center of mass?
Jun
5
awarded  Good Question
Jun
5
comment Defy gravity torques with gyroscopes?
What is keeping the platform from spinning about the rope?
Jun
5
comment How can there be really any instantaneous velocity?
+1 I automatically upvote anyone mentioning Gödel.
Jun
4
revised Calculating Pressure in CGS units
Formatted units and parameters
Jun
4
comment Bouncing ball time problem
Look at highered.mcgraw-hill.com/sites/dl/free/0073529281/365764/… for how to treat a sphere on plane (or other sphere) problem. Note that the contact penetration is $$x=\left( \frac{1}{d_1} + \frac{1}{d_2}\right) a^2$$ where $a$ is the contact patch radius, and $d$'s are the diameters of the contacting surfaces.
Jun
4
comment Bouncing ball time problem
It also depends on the diameter. In the end it is the non linear Hertzian contact properties that matter.
Jun
3
comment Deriving tensor in Euler's equations for rigid body rotation
The $\omega$ comes from vector differentiation on moving coordinate frame.
Jun
2
comment Deriving tensor in Euler's equations for rigid body rotation
Actually each infinitestimal mass does not have a mass moment of inertia so you have $${\rm d}I = -{\rm d}m [\vec{r}\times][\vec{r}\times]$$ as a starting point, and integrate over the volume.
Jun
2
comment Deriving tensor in Euler's equations for rigid body rotation
Funny how MIT just glosses over this part of the derivation in ocw.mit.edu/courses/aeronautics-and-astronautics/…
Jun
2
comment Deriving tensor in Euler's equations for rigid body rotation
Title should be deriving the rate of change of the inertia tensor.